Process for the preparation of fiber-containing plaster products

ABSTRACT

IT IS KNOWN TO PREPARE PLASTER PRODUCTS CONTAINING GLASS OR ROCK WOOL FIBERS, AS REINFORCING COMPONENTS, BUT SO FAR IT HAS NOT BEEN POSSIBLE TO OBTAIN AN EVEN DISTRIBUTION OF RELATIVELY LONG FIBERS THEREIN. ACCORDING TO THE INVENTION THEREIS PROVIDED A PROCESS FOR PERPARING SUCH PRODUCTS WHEREIN GLASS WOOL AND/OR ROCK WOOL IS CARDED, ADDING PLATER POWDER TO THE FIBERS AS THEY ARE CARDED TO PROVIDE A DRY COMPOSITION WHICH IS MIXED WITH WATER AND USED FOR CASTING.

g- 8, B. RUSTAN 3,682,670

PROCESS FOR THEPREPARATION OF FIBER-CONTAINING PLASTER PRODUCTS Filed July 2, 1970 INVENTOR,

T TQRNEYS United States Patent Oflice Patented Aug. 8, 1972 3,682,670 PROCESS FOR THE PREPARATION OF FIBER- CONTAINING PLASTER PRODUCTS Birger Rustan, Drammen, Norway, assignor to B. Rustan A/ S, Drammen, Norway Filed July 2, 1970, Ser. No. 51,863 Int. Cl. C04b 11/00 US. Cl. 106-110 3 Claims ABSTRACT OF THE DISCLOSURE It is known to prepare plaster products containing glass or rock wool fibers as reinforcing components, but so far it has not been possible to obtain an even distribution of relatively long fibers therein. According to the invention there is provided a process for preparing such products wherein glass wool and/ or rock wool is carded, adding plaster powder to the fibers as they are carded to provide a dry composition which is mixed with water and used for casting.

This invention relates to a process for the preparation of fiber-containing products, particularly boards and other construction elements, based on plaster, In particular it relates to the preparation of fire-inhibiting plaster products containing glass and/ or rock wool fibres as reinforcing and fire-inhibiting components.

In the preparation of plaster-products containing glass and/or rock wool fibres it is a problem to obtain a distributi'on of the fibres in the plaster since they have a tendency to tangle and form lumps or balls. Thereby one does not obtain the desired favourable effect, viz. mechanical strength and fire safety, which is dependent upon the fibres being evenly distributed in the plaster composition used for casting and thereby in the cast products. It is possible to cut up the fibres into such short length that they can not tangle, but the products prepared therefrom do not have quite satisfactory mechanical strength.

An effort to solve this problem has been described in German Pat. No. 934,395 which relates to the preparation of a plaster products containing glass fibres as filler. According to the patent the glass fibres are cut up and bound together by means of a water soluble binder. The resulting fibre bundles are introduced into and mixed with the preferably wet plaster to obtain an even distribution of the fibres in the ready cast plaster object. The process according to the patent is inconvenient, and in particular the mixing of the fibres with the plaster composition is time requiring. Further, the introduction of the binder may be undesired in the finished plaster products.

The object of the present invention is to provide a process obviating the above mentioned problems of tangling in a better and more effective manner than previously. Thus, according to the invention there is provided a process for the preparation of plaster products, particularly boards and other construction elements, containing glass and/or rock wool fibres as reinforcing and fire-inhibiting components, and, if desired, binders and/ or other additives. The process is characterized in that glass wool and/or rock wool is carded, and during the carding plaster powder is added to provide a dry composition which is mixed with water to provide a wet composition which is used for the casting of the desired products. The final casting may be carried out in a per se known manner.

If the plaster powder is not added to the fibres until after the carding has been finished, the fibres will easily form lumps without providing an even mixture of fibres and plaster powder.

It has been found particularly suitable to use both rockwool and glass wool in the process, since the rock wool will give the product the best fire-inhibiting effect, while the glass wool will give it the best mechanical strength. By using both these types of fibres in suitable amounts products may be obtained having very good fire-inhibiting properties together with high bending strength and tensile strength. Upon the influence of high temperatures, for instance above about 600 C., the glass will melt and bind together the rock wool so that the product will also be very strong even under such conditions.

The mixing of the dry plaster/fiber mixture with water is suitably performed by introducing the dry mixture into a vessel filled with water in such an amount that the water and the plaster/fibre mixture both reach the same height in the vessel. The aqueous mass obtained is suitable for casting.

A suitable binder which may be added to the water or the aqueous mass is polyvinyl acetate, but other types of binders and other additives may also be employed.

Equipment for performing the process is illustrated diagrammatically in the drawing where 1 and 2 are scales/dosing equipment for rock Wool and glass wool, 3 is a conveyer belt for rock wool and glass wool, 4 is scale/dosing equipment for plaster, 5 is carding a roller on which the wool is carded and plaster applied, 6 is a conveyer belt for carded wool with plaster, and 7 is a wet mixing vessel. To the latter is suitably added in advance the proper amounts of water, binder and possible other additives before the dry mixture of rock wool and glass wool and plaster is added. From the vessel 7 the wet mass is passed to moulds (not shown) in which the final product is cast. If desired a post treatment is carried out, for instance drying, pressing, coating etc.

The following example will illustrate the invention further.

EXAMPLE .A mixture of 0.2 kg. rock wool and 0.1 kg. glass wool were carded and mixed with 0.9 kg. plaster powder during the carding. The dry mixture obtained was introduced into 1 liter of water containing minor amounts of additives. The wet mass was used for casting of boards in moulds made of carton.

The process according to the invention may be employed for the preparation of a number of different plaster products, particularly for furniture, and in the shipbuilding and construction industries where fire-inhibiting materials -are desired, for instance for chairs, tables, boards, elements, doors, canals etc. The products have high mechanical strength, they are not combustible and hold well on screws and nails.

In the foregoing example the plaster powder employed is plaster of Paris or calcium sulphate hemihydrate. As will be apparent to the art skilled from the specification other plastic materials can be used which have properties similar to those of plaster of Paris.

What is claimed is:

1. A process for preparing a plaster product containing fibers selected from the group consisting of glass wool fibers and rock Wool fibers evenly distributed in the plaster product, which comprises carding the fibers, add- 3 4 ing plaster powder to the fibers during the carding to pror References Cited vide a dry composition, mixing the dry composition with UNITED STATES PATENTS water to provide a wet composition and casting of the 2,871,134 1/1959 Loechl 106-110 plaster product with the wet composition.

2. The process according to claim 1, wherein a binder 5 I is added to the water or wet composition. JAMES POER Pnmary Exammer 3. The process according to claim 1, wherein the US. Cl. X.R.

plaster powder is plaster of Paris. 106-111 UNITED STATES IATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,682,670 Dated August 8, 1972 Inventor s) Birger RU STAN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Insert in the Heading of the Patent, efter the Serial No.

Claims priority, application Norway, July 2, 1969, 278l/69-.

Signed and sealed this 9th day of April 1 97M.

(SEAL) Attest:

EDWARD I I.FLETCHER,JR. V C. MARSHALL DANN Attesting Officer 7 v Commissioner of Patents :ORM PC4050 (10459) USCOMM-DC oos'Ie-pu .5. GOVERNMENT PRINTNG OFFICE: l9. 0"36-33, 

